stabilize app: deprecate HIL from build system

* the hil build has not been maintained since feb
  and would require fundamental changes to the new
  ivory/tower architecture. reinstate it if we
  ever decide to support it again.
mk: disable gcc warnings for parentheses and unused-variable; ivory causes these

* kinda evil but we dont write c by hand anymore, right? so its ok.
ArduCopter: deprecate arducopter sketch build (unsupported)